The OH137 provides low output when (S) magnetic field is present.
A resistor from 1k-10k is recommened between VCC and Output, and a capacitor might be nedeed between ground and output depending in your application.

Features:
Operating Voltage: from 4.5 to 12VDC.
Ouput: Low (25mA) with proper magnetic orientation and field strengh.

Includes:
1x OH137 Hall Effect Unipolar Sensor.